Scientists create the world’s most powerful miniature laser in the laboratory

This article was originally published in The Conversation. Read the original article.

Gamma-ray bursts, intense bursts of light, are the brightest events ever observed in the universe, lasting no more than seconds or minutes. Some are so luminous that they can be seen with the naked eye, like the burst GRB 080319B discovered by NASA's Swift GRB Explorer mission on March 19, 2008.

But even though they are so intense, scientists do not Do I really know what causes the gamma-ray bursts. There are even people who believe that some of them could be messages sent by advanced alien civilizations. Now, for the first time, we have managed to recreate a mini version of a gamma-ray burst in the laboratory, opening a new way to investigate its properties. Our research was published in Physical Review Letters .

An idea for the origin of gamma ray bursts is that they are somehow emitted during the emission of jets of particles released by massive astrophysical objects, such as black holes. This makes the gamma ray bursts extremely interesting for astrophysicists; its detailed study can reveal some key properties of the black holes from which they come.

Beams released by black holes would be composed mainly of electrons and their companions "antimatter", positrons: all particles have antimatter equivalents that are exactly identical to them, only with opposite charge. These beams must have strong and self-generated magnetic fields. The rotation of these particles around the fields produces powerful bursts of gamma radiation. Or, at least, this is what our theories predict. But we do not really know how the fields would be generated.

Unfortunately, there are a couple of problems when studying these bursts. Not only do they last for short periods, but, most problematically, they originate in distant galaxies, sometimes even a billion light years from Earth (imagine one followed by 25 zeros, this is basically what a billion light years are in meters).

That means you trust to look at something incredibly far away that happens randomly, and lasts only a few seconds. It's a bit like understanding what a candle is made of, just by having flashes of candles that light up from time to time thousands of kilometers away from you.

The most powerful laser in the world

It has recently been proposed that the best way to determine how gamma-ray bursts occur would be to imitate them in small-scale reproductions in the laboratory, reproducing a small source of these beams positrons of electrons and observing how they evolve when left alone. Our group and our partners from the USA The United States, France, the United Kingdom and Sweden recently managed to create the first small-scale replica of this phenomenon using one of the most intense lasers on Earth, the Gemini laser, hosted by the Rutherford Appleton laboratory. in the United Kingdom.

How intense is the most intense laser on Earth? Take all the solar energy that hits the entire Earth and squeeze it in a few microns (basically the thickness of a human hair) and you will get the intensity of a typical laser shot in Gemini. By firing this laser at a complex target, we were able to launch ultra-fast and dense copies of these astrophysical planes and make ultra-fast movies about how they behave. The decrease of these experiments is dramatic: take a real jet that extends even for thousands of light years and compress it to a few millimeters.

In our experiment, we were able to observe, for the first time, some of the key phenomena that play an important role in the generation of gamma-ray bursts, such as self-generation of magnetic fields that lasted a long time. They were able to confirm some important theoretical predictions about the strength and distribution of these fields. In summary, our experiment confirms independently that the models currently used to understand gamma-ray bursts are on the right track.

The experiment is not only important for studying gamma-ray bursts. Matter made only of electrons and positrons is an extremely peculiar state of matter. Normal matter on Earth is predominantly composed of atoms: a heavy, positive nucleus surrounded by clouds of light and negative electrons.

An artist impression of an explosion of gamma rays. NASA

Due to the incredible weight difference between these two components (the lightest core weighs 1,836 times the electron) almost all the phenomena we experience in our life Everyday comes from the dynamics of electrons, which are much faster in responding to any external input (light, other particles, magnetic fields, whatever) than the nuclei. But in an electron-positron beam, both particles have exactly the same mass, which means that this disparity in the reaction times is completely erased. This brings a number of fascinating consequences. For example, sound would not exist in an electron-positron world.

So far so good, but why should we worry so much about events that are so far apart? There are many reasons, by the way. First, understanding how gamma-ray bursts are formed will allow us to understand much more about black holes and thus open a large window on how our universe was born and how it will evolve.

But there is a more subtle reason. SETI-Search for Extra-Terrestrial Intelligence seeks messages from extraterrestrial civilizations trying to capture electromagnetic signals from space that can not be explained naturally (it focuses mainly on radio waves, but gamma-ray bursts are also associated with such radiation). [19659003] Of course, if you put your detector to look for emissions from space, you get a lot of different signals. If you really want to isolate intelligent transmissions, you must first make sure that all natural emissions are perfectly known so that they can be excluded. Our study helps to understand the emissions of the black hole and the pulsar, so that, whenever we detect something similar, we know that it does not come from an alien civilization.

Gianluca Sarri, professor at the Faculty of Mathematics and Physics, Queen & B's University